With respect to the present state of the prior art on the subject, the object of the invention is to achieve the following aims:
to be able to work in narrowly confined locations, in particular in an urban environment where the overall dimensions of the apparatus must be as small as possible, causing the least possible inconvenience, PA1 to obtain reliable operation of the apparatus, without the risk of breakage of the apparatus, substantially whatever the conditions encountered on the terrain, PA1 that the apparatus should be as functional and simple as possible as regards construction and use, PA1 to permit limited manufacturing and operational costs, PA1 to allow optimum control and guiding of the drilling, in a simple and functional manner, PA1 to limit as far as possible the risks of disturbance of the subsoil during drilling of the hole by the apparatus. PA1 to produce the said starting region as an open shaft in the ground on a substantially vertical axis with a substantially constant horizontal section over the depth of the shaft, while being preferably insufficient for a man to be able to work towards the bottom of it with the said drilling assembly, PA1 in order to dig the hole, to displace the rod assembly, in the hole, by elements, in the direction of the hole, from an opening located in a front wall of the shaft, PA1 and to select the elements of the rod assembly so that they have an axial length less than the distance separating the said opening in the front wall of the shaft from the opposite rear wall. PA1 a framework suitable for being lowered, at least in part, into the shaft, PA1 drilling rod elements to be arranged end to end, being individually of a specific length, PA1 drilling drive means displaceable in the framework between two positions, forward and rear, in order to drive the drilling rod elements and to create, while advancing, an assembly of rod elements which are relatively rigid along a substantially horizontal axis, PA1 the said length of the elements constituting the said assembly of rod elements which is created being less than a width which the said framework has along the axis of the rod assembly. PA1 clamping means for clamping individually the last rod element(s) constituting the said drilling rod assembly, PA1 thrust means, for advancing the said rod assembly by compression, along its axis in the drilling direction, PA1 and loading/extracting means movable in the said framework between a high position and a low position in order, in one direction, to bring additional rod elements to the drilling drive means so as to lengthen the rod assembly and, in the opposite direction, to extract elements from the rod assembly, therefore to shorten it. PA1 clamp by means of the drive device the outer periphery of a rear element of the said assembly located in the shaft, PA1 to advance this element towards the hole, along the axis of the rod assembly, by a length corresponding substantially to the length of the element, PA1 and, while retaining the rod assembly already in the drilled hole in order to prevent it from moving back, to grasp another rear element of the rod assembly, and so on, element by element.
Until now it has been proposed, to drill an essentially horizontal hole in the ground, to use a drilling rod assembly comprising a succession of drilling rod elements arranged end to end along an axis and capable of being pushed forwards, in the ground, by a drilling drive device.
Thus, a drilling machine has already been used to sink, from the surface of the soil into the sub-soil, on an inclined path, a rod assembly constituted of a large number of drilling stems or rods, screwed end to end to one another, and each being several meters in length. The direction of penetration (that is to say, of the drilling head which is at the forward end of the rod assembly) can be relatively well adjusted, so that drilling takes place first flat and obliquely downwards, until the prescribed depth is reached, then drilling is continued in an essentially horizontal direction, still by means of the guiding of the drilling head.
For drilling, the rod assembly is pushed forwards by the drilling drive device fixed to the rod assembly at the front. This rod assembly is often driven in rotation, and/or, under the action of the water which escapes from the drilling head under high pressure. The materials encountered during drilling are then expelled, most often through an internal hollow passage provided through the rod assembly.
This process is used especially for laying pipe systems over long sections, for example of 100 meters or more.
Such a drilling apparatus, which among other things must have a mounting directed obliquely downwards to guide the rod assembly, is large and weighs at least two tonnes, since the weight of the drilling machine serves in part as a stop for the force serving for the forward compression of the rod assembly.
It is considered that known drilling apparatuses, a typical example of which has just been described, do not reasonably satisfy at least the essential aims assigned here.